Polymerization of vinyl monomers to prepare polyvinyl resins has been extensively researched and practiced. Economic competition in the thermoplastics manufacturing industry has created a marketplace in which the consumer enjoys a plethora of plastic products: however, there exists an ever increasing demand for lower priced, quality products. This widespread commercial success of thermoplastic products prepared from polyvinyl resins has generated incentive to search for more efficient methods of preparation.
In order to improve commercial preparation of thermoplastic products, efforts have been made to improve the polymerization processes which provide the feedstock polyvinyl resin. Various initiators and catalysts for polymerization processes have been taught.
Van Peski, U.S. Pat. No. 2,478,066 discloses hydrazone as a polymerization promoter for vinyl monomers, the reaction taking place at high temperature under pressurized conditions.
Conventional polymerization processes require relatively high temperatures to first initiate polymerization and then to provide for high rates of conversion of the monomeric unsaturate to the polymeric resin. Elevated temperatures degrade the resin thus adversely effecting the structural properties of the thermoplastic product.
In order to polymerize vinyl monomers at lower temperatures, azo and peroxide initiators have been taught. Howard, U.S. Pat. No. 2,610,293 discloses the use of both a hydrazone and a peroxide initiator in the polymerization of vinyl monomers. A disadvantage to the commercial use of volatile chemicals such as peroxides is that they are hazardous to use and production costs increase accordingly.
It would be highly desirable to be able to polymerize vinyl monomers under milder, safer and less costly polymerization conditions.